The Long Term Evolution (LTE) wireless communication standard maintained by the 3rd Generation Partnership Project (3GPP) is a leading standard for use in cellular-type wireless communication systems, between evolved NodeB (eNB) base stations and User Equipment (UE). Wireless communication for LTE, such as downlink communication from eNB to UE, is organized into Physical Resource Blocks (PRB) in time and frequency. An LTE system can be implemented with one of a range of bandwidths and current standards allow for transmission of between 6 and 110 PRBs pairs per 1 ms subframe. A PRB pair as used herein refers to a pair of PRBs located in time-adjacent 0.5 ms time slots of a subframe. A typical PRB pair transmitted on the downlink contains pilot signals, control information of the Physical Downlink Control Channel (PDCCH) and shared payload information of the Physical Downlink Shared Channel (PDSCH). In various implementations, the PDCCH can occupy up to four of the nominally fourteen symbol intervals of a given PRB pair. PDCCH information is received first and indicates to the UEs where they may find data within the PDSCH field following.
In practice the decoding of the PDCCH can take a significant amount of the time during which the PDSCH is being received. All of the PDSCH symbols in a subframe are therefore typically buffered in memory before de-interleaving can occur, and it is therefore acceptable for the PDSCH decoding to take all for the subframe. Legacy UEs may need to buffer up to a full set of up to 110 PRB pairs due to having large amounts of data to receive. This results in a relatively large buffer memory requirement and added expense for such UEs.
Currently, various solutions are being sought for providing for lower cost or limited capability (LC) UEs to operate within the LTE standard. These UEs may be intended for specific applications such as Machine-Type Communication (MTC) or Machine-to-Machine (M2M) applications. Such devices may be delay tolerant and may not require access to high data rates. Introduction of standards changes in order to accommodate the new category of UEs is possible. However, it is desirable that any such changes should be relatively easy to implement and should not adversely affect current levels of performance or system efficiency for legacy categories of UEs.
One proposed feature of LC UEs is that they may only support a limited number of shared downlink channel (PDSCH) Physical Resource Block (PRB) pairs (e.g. 6 or 15 PRB pairs) per subframe while still allowing use of the legacy downlink control channel (PDCCH) assignment mechanism. Such LC UEs would still be able to receive PDCCH information that may be contained in any PRBs across the full system bandwidth, but would only need to receive for example 6 PRB pairs per subframe of PDSCH. The PRBs designated for a LC UE do not have to be contiguous but may be distributed across the system bandwidth. This may provide a cost reduction for example by allowing for a possible reduction in post FFT buffer memory size for the LC UEs.
However, since the limited number of PRB pairs allocated for use by LC UEs is not generally known a priori, and since decoding of the PDCCH may take a significant amount of time, the LC UE is still generally required to buffer all PRB pairs. This represents a waste of resources since the majority of buffered data is unused by the LC UE.
Therefore there is a need for a method and apparatus for supporting downlink communication including blind detection by UEs, such as LC UEs, that is not subject to one or more limitations of the prior art.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.